OBJECTIVES: I. Analysis of the organization of immunoglobulin genes. II. a. Investigation of the reason for the discrepancy in quantities in T cells of immunoglobulin mRNA (about one half as much as in B cells) and cellular immunoglobulin (none to 1/100 as much as in B cells). b. Determination of the relationship of T-cell maturation, presence of terminal transferase (Baltimore, Nature 248 (1974) 409) and quantity and localization of kappa-mRNA. c. Study of several parameters of the regulation of immunoglobulin synthesis in B cells.